Behaviour of convective updraughts: A challenging problem for weather and climate models

Lead Research Organisation: University of Leeds
Department Name: School of Earth and Environment

Abstract

The aim of the project is: to improve the understanding of the physical processes that determine the time evolution of convective updraughts. For example, we believe that clouds are composed of thermals; see the schematic diagram below and compare with the photo of a real cloud. But how can this schematic model be represented as an idealised model that could form the basis of the representation in weather and global climate models? The PhD student will likely find this question to be interesting and challenging. Perhaps there is a different way of representing the clouds, as say plumes? Specific questions that need to be considered include: what is the size of the cloud core region and the amount of liquid in it, and how do these change with time? What is the interaction between this core region and the descending air at the edge of the cloud? What are the characteristics of the turbulent eddies that cause mixing, as well as the circulation of the whole cloud. These questions will be addressed by using simulations of both single clouds and collections of clouds.
The simulation of convective updraughts is particularly sensitive to model resolution. The PhD research will involve numerical experiments at 25 m resolution. At this resolution, mixing between convective clouds and their environment is well resolved. The availability of a new high-resolution model (the Met Office NERC cloud model, MONC) that can efficiently run on the latest generation of supercomputers, now makes it possible to perform such simulations on large domains, such that a collection of clouds can be studied. This is a very exciting development: the figure below shows an example of the detailed cloud structures that can be simulated with such a model. Numerical experiments will likely include studies of idealized single clouds, as well as multiple clouds in a setting which is based on field campaigns. The use of these field observations provides an important check on the realism of the model simulations.

Publications

10 25 50
 
Title LES model setup for field campaign case study 
Description I have developed a model setup to replicate conditions from a well-known field campaign, which can be used primarily using the Met Office and NERC Cloud model 'MONC' (a large-eddy simulation). 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? No  
Impact Scientists in the field use other model setups for well-known field campaigns that focus on atmospheric convection, however this particularly case study (COPE - the Convective Precipitation Experiment) is not one that is commonly used as it is less well known. Once this model setup has been published, it can be used by others as the initial conditions for future simulations. 
 
Description Public engagement talk for Royal Meteorological Society 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact The Royal Meteorological Society's Yorkshire Local Centre host regular public engagement talks for their members. These talks are aimed at a general audience, as many RMetSoc members do not have an academic background in meteorology and consider it more as a hobby. I had the opportunity to present my PhD work, as well as explain the fundamentals of numerical weather prediction, to such an audience in April 2018.
Year(s) Of Engagement Activity 2018